160 TANNINS. 



billa^ corresiDond exactly to gallotannic acid, and all that has been 

 said of the latter is equally true of the foi^mer. They ai-e always 

 accompanied hj gallic acid in the materials that yield them. 



Some of these also contain the so-called ellago-tannic acid, 

 which is found in notable quantities in myrobalans, divi-divi and 

 bablah fruits.' 



This ellago-tannic acid, which, as far as Loewe's experiments 

 show, is not a glucoside, differs from gallotannic acid in yielding 

 ellagic in the place of gallic acid, a change that can be brought 

 about by water alone at a temperature of 108° to 110°. Ellagic 

 acid can be obtained in sulphur-j^ellow crystals, which are almost 

 insoluble in boiling water or in ether, and sparingly soluble in 

 alcohol. Xotwithstanding, however, its slight solubility in ether, 

 small quantities can be removed from aqueous solution by shak- 

 ing with that liquid. Ferric chloride produces first a green, then 

 an inky colouration. It is soluble in potash, and is precipitated 

 by acetate of lead from an alcoholic solution in the form of lead- 

 salt, containing 63 per cent, of oxide. The dry substance heated 

 with zinc dust yields the hydrocarbon ellagene (C^^^H^^), Avhich 

 cannot be combined with picric acid. 



Whether ellago-tannic acid has been prepared in a state of 

 jDurity, and whether it is identical with punico-tannic acid,^ are 

 questions Avhich we may for the present leave out of considera- 

 tion. According to Eembold, the latter also yields ellagic acid. 

 Special methods for the estimation of these two substances have 

 not as yet been published. 



For nymphasa-tannic acid see § 161. 



Gallotannic and gallic acids also occur in tea, accompanied by 

 quercetin (possibly present in sumach also, § 152), and by the so- 

 called boheic acid.* The latter is not thrown down Avhen acetate 

 of lead is added to a hot infusion of tea, but is precipitated on 



Chem. xii. 12S, 1873 (Journ. Chera. Soc. xxvi. 748) ; xiv. 46 (tannin of 

 knoppern-galls). 



1 Compare Godeffroy, Zcit.schr. d. Oesterr. Apoth.-Ver. 132, 1879 (Year-book 

 Pharm. 215, 1879). 



- Compare (iiinther, loc. r.'it. Also my observations in the Jahresbericht f. 

 Pharm. 192, 1875 ; and Loewe, Zeitschr. f. anal. Chem. xii. 128 ; xiv. 35, 44. 



•* Annal. d. Chem. und Pharm, cxliii. 285, 1867. I may observe that in the 

 pomegranate bark also the substance yielding ellagic acid is accompanied by 

 gallotannic acid, and that llembold obtained sugar by the decomjiosition of 

 the former. 



■* Compare Hlasiwetz, Annal. d. Chem. und Pharm, cxlii. 233. 



